Pneumonia Bacterial Pathogens Flashcards
Strep pneumo risk factors
alcohol/drug intoxication causing cerebral impairment depressing the cough reflex and increasing aspiration; abnormality of the reps fact including injury, infection, and obstruction; abnormal circulatory dynamics; splenectomy, sickle cell, HIV
How is sickle cell a risk factor for strep pneumo
auto-splenectomy. Encapsulated pathogens like strep pneumo are typically cleared by the spleen
Strep pneumo virulence factors
capsule, lipoteichoic acid (activates complement, induces cytokine production), IgA protease enhancing ability to colonize mucosa
How is strep pneumo diagnosed
Urinary antigen, Gram stain and culture; it is optochin sensitive and shows Quellung reaction
What does strep pneumo look like on gram stain
Lancet-shaped, gram positive diplococcus
Treatment options for Strep pneumo
Ceftriaxone, Amoxicillin, Levofloxacin, Azithromycin
Strep pneumo vaccines
Pneumovax (23 type) provides 5yrs of protection used for people 65+ and those at heightened risk
Prevnar (13 types) recommended for children and infants
Herd Immunity
if most of the population receive a vaccine then those who do not are protected because they are surrounded by people who will not get the disease
What populations usually get mycoplasma pneumonia
military recruits, prison inmates, and school aged children
Mycoplasma pneumonia’s pathogenesis
Adhesin binds to ciliated epithelial cells and causes reduced ciliary clearance
Diagnostic methods for myoplasma infection
Cold agglutinins (IgM), serology, grown on Eaton agar, PCR on respiratory secretions
Best treatment for Mycoplasma
Levofloxacin, Azithromycin, or Doxycycline
Why does penicillin not work to treat mycoplasma
Mycoplasma has no cell wall
Chlamydia pneumonia
similar presentation to mycoplasma (walking pneumonia) except more common in older people (40ish); has no good diagnostic test; treat with Doxycycline
Psuedomonas typical habitat
common in hospital; lives in wet environments and can be problematic for patients on ventilators; also in soil and plants
Pseudomonas microbiologic features
non-fermentative, motile, oxidase-positive, elaboration of green pigment; smells fruity
H. influenza microbiologic features
small, pleomorphic; facultatively anaerobic, nonmotile
Klebsiella pneumonia microbiologic features
lactose fermenting, indole-negative; incapable of growth at 10C
A. baumanii microbiologic features
gram-negative coccobacilli, non-motile, strictly aerobic, catalase positive, oxidase-negative
Microplasma pneumonia virulence factor
Adhesin
Ps. aeruginosa virulence factor
endotoxin and exotoxin A (enzyme blocks protein synthesis by inactivating EF-2 by ADP ribosylation), elastase, leucocidin, lemolysins, alginate, exoenzyme S
Staph aureus virulence factor
enterotoxin
S. pneumonia virulence factor
capsule
Pseudomonas effects
can cause extensive vasculitis with thrombosis and hemorrhage with necrosis
Antibiotics for psuedomonas
Cefepime, Zosyn, Meropenem, Ciprofloxacin
Legionella location
contaminated water source (hotel/hospital showers, hot tubs, AC units)
Legionella signs and symptoms
fever, dry cough, diarrhea, confusion, Hyponatremia in older smoking population with comorbidities
Legionella Diagnostic tools
CXR, silver stain, culture on charcoal yeast extract agar enriched with cysteine and iron, urinary antigen testing, direct fluorescent antibody
Pontiac fever
acute, febrile self limited illness; symptoms include fever, malaise, chills, fatigue, HA, no respiratory complaints; no abnormalities on CXR; usually requires no treatment
Legionella Virulence factors
intracellular (results in decreased clearance and can parasitize and live in alveolar macrophages); cell wall endotoxin (major virulence factor; causes host inflammatory response which causes lung damage)
Treatment for Legionella
Levofloxacin and Azithromycin
Crackles
scratchy sounds caused by accumulation of fluid/white cells/bacteria in alveolar and interstitial spaces
Bronchial breath sounds
dense consolidation of lung parenchyma results in transmission of large airway noises to the periphery
Dullness to percussion
normal, air filled tissue has been displaced by fluid or infiltrated with white cells and bacteria
Increased tactile fremitus
consolidation alters transmission of air and sound.
Lung consolidation
occurs when lung parenchyma becomes engorged with fluid or tissue usually in the presence of pneumonia
Organisms that cause community acquired pneumonia
staph aureus, Hemophilus influenza, klebsiella pneumonia, moraxella catarrhalis
What bacteria causes currant jelly sputum, often seen in chronic alcoholics and malnourished
Klebsiella pneumonia
What bacteria is seen in post-viral respiratory infections
Staph aureus
Bacteria very common cause of hospital acquired PNA
Staph aureus
Bacteria with 6 serotypes, encapsulated and non, gram - coccobacillary
H. influenza
Bacteria grows on chocolate agar, requires factors V and X for growth
H. influenza
Bacteria that have complications including abscess and necrotizing PNA
Staph aureus and Klebsiella pneumonia
Bacteria with common drug resistance
S. aureus and K. pneumonia
Bacteria where amoxicillin is used for mild infection and ceftriaxone is used for serious infections
H. influenza
Bacteria where capsule is one of the major virulence factors
H influenza and K. pneumonia
Bacteria that also causes otitis media, epiglottitis, and meningitis
H. influenza
Bacteria whose vaccine incorporates the capsular polysaccharide b; and antibodies against capsule are protective
H. influenza
Common bacterial cause of acute exacerbations
H influenza and M. catarrhalis
Hospital acquired pneumonia risk factors
severe underlying disease, immunosuppression, prolonged antibiotic therapy, invasive devices such as IV catheters, mechanical ventilation
Difference between hospital acquired and health care associated pneumonia
HAP acquired during hospital stay; HCAP is hospitalization of at least 2 days within 90days; received IV therapy, wound care, or chemo in 30days; resident of nursing home; has hemodialysis
Most common organisms to cause HCAP
Pseudomonas aeruginosa and Staphylococcus aureus
Alpha hemolysis
seen in strep pneumo; shows dark red outline on blood agar
Beta hemolysis
seen in staph pyogenes; looks bright yellow on blood agar
Quellung reaction
antibodies to capsule material causing swelling
Optochin
used to distinguish S. pneumo (sensitive) from viridans strep
Step pneumo invasion
can alter vascular permeability to allow access to blood stream and cause bacteremia; can also directly invade endothelial cells; can cross blood brain barrier by binding to cerebral capillaries and cause meningitis
Strep pneumo virulence factors
capsule (resists phagocytosis), pili (used for bacterial adhesion to epithelial cells), cell wall components (techie acids and lipotechoic acid that cause inflammatory response)
Mycoplasma facts
lack a cell wall, smallest free-living organism, can cause primary atypical pneumonia; pleomorphic with polar structure
Mycoplasma virulence
attaches to surface of respiratory epithelia, and the lipoproteins interact with alveolar macrophage Toll-like receptors activating the production of inflammatory cytokines
Chlamydia pneumonia pathogenesis
transmitted via respiratory droplets or secretions, gradual onset of cough leading to pneumonia, can range from asymptomatic to severe, most common in school age children
Chlamydia pneumonia extrapulmonary associations
associated with chronic atherosclerotic disease
Legionella
Typically effects elderly, immunocompromised, heavy smokes, alcoholics, and others with compromised lungs; generally spread by fomites and vehicles (water), can survive community water treatment, usually occurs in isolated incidence but associated with mass outbreaks
Legionella virulence factors
replicates in alveolar macrophages after inhalation; it avoids phagosome-lysosome fusion by creating a specialized vacuole that resembles the ER of the host and supports bacterial replication (wild type and Dot/Icm - type IV secretion system)
Staph aureus micro
colonize the nasal passages but can be found on the skin; form large yellow colonies on rich agar medium; catalase +, coagulase +, hemolytic
Staph epi micro
colonizes the skin; forms small white colonies on rich agar medium; catalase +, coagulase -, non-hemolytic
Primary infections caused by staph aureus
Pneumonia and Meningitis
Primary infections by staph epi
usually nosocomial infections of implants
Pathogenesis of staph aureus
many virulence factors including adhesins, invasins, antiphagocytic surface factors, immunologic decoys, lytic toxins, exotoxins, and abx resistance
H. flu virulence
Capsule polysaccharide (serotype B)
H flu vaccine
Hib - type b capsular polysaccharide conjugated to a carrier protein (diphtheria) - given to children 2-15 months
Pseudomonas micro
important nosocomial pathogen especially in patients with leukemia, cystic fibrosis, and extensive burns; has ability to survive and proliferate in water
Klebsiella micro
large capsule, no one antigen is associated with disease; causes lobar pneumonia; opportunistic infections
Enterobacter micro
opportunistic pathogens, nosocomial infections in patients on anitbiotics
Klebsiella staining
negatively stained with India ink revealing the cell wall
Strep pyogenes facts
Group A Strep (GAS) beta hemolytic - strep throat; causative agent of numerous local and systemic disease and post-disease sequelae; can cause necrotizing fasciitis, shock, sequelae including acute rheumatic fever or glomerulonephritis
Strep agalactiae facts
Group B strep (GBS) beta hemolytic
Strep pyogenes pathogenesis
M proteins (resist phagocytosis), hyaluronic acid capsule, adhesins, invasins, exotoxins, strep pyrogenic exotocins
